Tilt-adjustable head rest having ratcheting mechanism

ABSTRACT

A tilt-adjustable head rest assembly (10) includes a hollowed headrest body (12) pivotally connected to a U-shaped mounting post (14). A ratcheting mechanism (104) is disposed within the headrest body (12) and includes a ratchet (108) interacting with a rack of ratchet teeth (106). The ratchet (108) has an elongate U-shaped support member (112) pivotally carrying a pawl member (110). An extension spring (116) extends between the pivot pin (114) and the support arm (112) for selectively biasing the pawl member (110) between an upstanding operable position and a knocked-down inoperable position.

TECHNICAL FIELD

The invention relates to tile-adjustable headrests and more particularlyto such headrests having a ratcheting mechanism for controlling theangular position of the headrest.

BACKGROUND OF THE INVENTION

Various headrests are known to the art which include a headrest bodypivotally coupled to a mounting post for enabling the headrest body topivot in a forward and rearward direction to achieve a desired positionof angular adjustment chosen by the user. Such headrests are also knownto include various ratcheting detente mechanisms which allow theheadrest to pivot forwardly but limit its rearward pivotal movement forsafety reasons. Numerous examples of such headrests are shown in priorart U.S. Pat. Nos. These include: 4,378,898 to Maruyama, granted Feb. 1,1983; 4,558,903 to Takagi, granted Dec. 17, 1985; 4,640,549 to Yokota,granted Feb. 3, 1987; 4,674,797 to Tateyama, granted Jun. 23, 1987;4,678,232 to Ishida et al, granted Jul. 7, 1987; 4,733,913 to Tateyama,granted Mar. 29, 1988; and 4,830,434 to Ishida et al, granted May 16,1989.

Many of these prior art mechanisms are complicated in design and requirenumerous linkages and the interaction of several parts for the operationof the ratchet mechanism. Each of these ratchet mechanisms includes apawl member pivotally supported by a pawl carrying support member forenabling the pawl to interact with a series of associated ratchetingteeth of a rack. These devices further include a spring connected at oneend to the pawl and at the other two a support for biasing the pawltoward an operational position into engagement with the teeth. In allcases, however, the pawl is supported in cantilever fashion by thesupport member and as such is subjected to torsional forces applied bythe spring. Over time, this may affect the performance of the detentmechanism.

SUMMARY OF THE INVENTION AND ADVANTAGES

An adjustable headrest assembly includes a mounting post having ahorizontal portion, a headrest body disposed about said horizontalportion , and pivot connection means for connecting the headrest bodypivotally to the mounting post for enabling the headrest body to pivotrelative to the mounting post. Ratcheting means act between the mountingpost and the headrest body for permitting the headrest body to pivot inone direction while selectively locking the headrest body againstreverse pivotal movement The ratcheting means includes a rack disposedon one of the headrest body and mounting post and having a plurality ofdirectional teeth and a ratchet disposed on the other of the headrestbody and mounting post for engaging the rack teeth to control themovement of the headrest body. The characterizing feature of theassembly is the construction of the ratchet. The ratchet is comprised ofa support member having a pair of parallel spaced side wall portions, apawl disposed between the side wall portions, and pivoting means forpivotally coupling the pawl to each of the side wall portions forenabling the pawl to pivot relative to the support member.

One advantage of this invention is that fewer parts are required toconstruct the mechanism. Another advantage is that the pawl is supportedon both sides for better performance.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a front view of a preferred embodiment of the invention shownpartially broken away and with the headrest body tilted forwardly;

FIG. 2 is a perspective view of the invention shown partially brokenaway;

FIG. 3 is a cross-sectional view taken along lines 3--3 of FIG. 1 butshowing the headrest body tilted rearwardly;

FIG. 4 is a cross-sectional view taken along lines 4--4 of FIG. 1 butshowing the headrest body tilted rearwardly;

FIG. 5 is a cross-sectional view taken along lines 5--5 of FIG. 1 butshowing the headrest body tilted rearwardly;

FIG. 6 is an exploded perspective view of a preferred detent mechanismof the present invention;

FIG. 7 is an enlarged fragmentary cross sectional view showing theheadrest body tilted between two positions of angular adjustment;

FIG. 8 is a cross-sectional view taken along lines 8--8 of FIG. 2;

FIG. 9 is an enlarged fragmentary cross-sectional view of the sidesnap-coupling joining the headrest shell to the base; and

FIG. 10 is an enlarged fragmentary perspective view of the front andrear snap couplings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An adjustable headrest assembly constructed according to a presentlypreferred embodiment of the invention is generally shown at 10 in FIG. 1and includes a headrest body 12 mounted to mounting post means (ormounting post) 14 for attachment to a seat (not shown).

The mounting post means 14 is a generally U-shaped support having a pairof spaced apart and parallel extending legs 16 integrally joined attheir upper ends by a generally horizontal transverse cross memberportion 18. The mounting post 14 is constructed from a single piece ofcylindrical metal rod having a generally circular cross section whichhas been bent into the U-shape to form the legs 16 and cross member 18.The legs 16 are formed on their rearward side with a plurality ofnotches 20 which are designed to engage a vertical adjustment mechanism(not shown) of the seat in known manner. The cross member 18 is formedwith a central flattened region 22 located approximately midway betweenthe legs 16 and presenting a pair of parallel flats 24 which are offsetor angled with respect to the legs 16 (FIG. 3) for reasons describedbelow. The flattened region 22 is formed during a coining operation andpreferably prior to bending the post 14 into its U-shape.

The headrest body 12 is comprised of a hollow elongate core 26 extendinghorizontally along the cross member 18 and fabricated of rigid organicpolymeric material defining a cavity 28 within the headrest body 12. Thecore 26 includes separate and distinct upper and lower first and secondbody sections 30, 32 having self-locking snap-together coupling means 34for automatically locking the first body section 30 into retainingengagement with the second body section 32 upon application of acompressive assembly force applied to the body sections 30, 32 to forcethem into engagement with one another and to capture the horizontalportion 18 of mounting posts 14 between the sections 30, 32.

The upper section 30 is formed as a hollow shell or cover member and hasa top wall 36, a pair of side wall portions 38, and front and rear wallportions 40, 42. The cover 30 is open at the bottom. The lower section32 is formed as a generally planar base member having an upper surface44 engaging the extended free ends of the side wall portions 38 andfront and rear wall portions 40, 42 to close the cavity 28. The basesection 32 also has a lower surface 36 defining an underside of theheadrest body 12. As shown in FIG. 2, the base section 32 has a pair ofslot-like elongate openings 48 through which the legs 16 extend out ofthe cavity 28.

The self-locking snap-together coupling means 34 comprises mutuallyengagable female and male members formed as integral portions of thebody sections 30, 32. As shown best in FIG. 1, the mutually engagableportions comprise a pair of left and right snap couplings 50, shown indetail in FIG. 7, and a pair of front and rear snap couplings 52, shownin detail in FIG. 8, both of which are external to the headrest cavity28. Each of the left and right couplings 50 includes flexible malespring finger latch 54 formed integrally with the lower section 32 andextending upwardly therefrom for snap-together locking engagement with afemale boss or catch 56 formed integrally on the left and right sidewall portions 38 of the upper body section 30. As shown best in FIG. 7,the spring finger latch 54 includes an upstanding shank 58 extendingfrom the upper surface 44 of the base 32 and terminating with anenlarged locking head 60. Each head 60 is formed with a camming surface62 and a locking shoulder 64. The catches 56 extend outwardly of theleft and right side wall portions 38 of the upper section 30 and havegenerally vertical passageways or channels 66 extending therethrough forinsertably accommodating the spring finger latches 54. The catches 56also include a locking shoulder 68 adjacent the channel 66 for lockablyengaging the locking shoulder 64 of the enlarged head 60 when assembled.Upon forcing the upper section 30 into engagement with the lower section32, the cam surface 62 engages the walls of the channel 66 and causesthe spring finger 54 to elastically deflect enabling the enlarged head60 to enter the channel 66. Once the head 60 passes through the channel66, the elasticity of the spring finger latch 54 causes the latch 54 toreturn to its undeflected condition and the locking shoulder 64 of thelatch 54 to lockingly engage the shoulder 68 of the catch 56, as shownin FIG. 9.

The front and rear snap couplings 52 (FIG. 10) are similarly constructedand include an elastic male spring finger latch 70 extending up from thelower body section 32 and engaging corresponding catches or bosses 72formed integrally with and extending outwardly of the front and rearwall portions 40, 42 of the upper body section 30. The latches 70 eachhave a similar shank portions 74 and enlarged locking heads 76 formedwith a camming surface 78 and locking shoulder 80. The catch 72,however, has an open U-shaped passageway or channel 82 for guiding thelocking shoulder 80 of the spring finger latch 70 into snap-togetherengagement with a corresponding upper surface locking shoulder 84 of thecatch 72. As shown in FIG. 1, the front pair of snap couplings 52 areoffset in spacing slightly from the rear pair of snap couplings toassure that the upper section 30 can be connected to the lower section32 in one way only. The front and rear snap couplings 52 operate in allother respects identically to the left and right snap couplings 50.

A headrest cushion 86 is disposed about the headrest core or body 26 forcomfort and comprises a layer of foam 88 and an overlying decorativecover 90 disposed about the outer surface of the upper section 30 andextending beyond the lower section 32 as shown in FIG. 3. In thismanner, the under-side 46 of the head rest body 12 is concealed but notcovered by the headrest cushion 86. The headrest cushion 86 ispreferably disposed about the core 26 using foam-in-place technology inwhich the foam 86 is introduced in liquid form between the cover 90 andcore 26 and then cured to assume the desirable headrest shape. Theheadrest cushion 86 is devoid of any foam 88 in the region of the snapcouplings 50, 52 to ensure their proper functioning.

Referring now to FIGS. 2 and 4, the headrest assembly 10 furtherincludes pivot connection means 92 formed integrally with the upper andlower sections 30, 32 for directly pivotally connecting the headrestbody 12 to the mounting post 14 to enable the headrest body 12 to pivotrelative thereto in either a forwardly or rearwardly direction. Thepivot connection means 92 comprises a plurality of interlocked rear andlower saddle portions 94, 96 formed integrally with the upper and lowercore sections 30, 32, respectfully, and extending into the headrestcavity 28 and straddling the horizontal cross member 18 on oppositesides thereof to pivotally couple the sections 30, 32 of the headrestbody 12 to the mounting post 14. The upper saddle portions 94 extendbetween the front 40 and rear 42 walls of the upper section 30, as bestillustrated in FIG. 4, bridging the walls 40, 42 and providingstructural rigidity (i.e., crush strength) to the headrest body 12.

The extended free ends of the upper saddles 94 are each provided with agenerally semicircular U-shaped recess 98 for receiving the cross member18 within the recesses 98 with a portion of the saddles 94 extendingbeyond the cross member 18 (i.e. straddling) as shown best in FIGS. 2and 4. The saddles 96 of the lower section 32 each include self-lockingsnap-on retaining means for engaging and retaining the cross member 18attached to the lower section 32. The retaining means comprises a pairof flexible spring arms 100 which are spaced from one another and definea socket 102 therebetween. The opening into the socket 102 is smallerthan the diameter of the cross member 18. However, forcing the arms 100against the cross member 18 causes the arms 100 to deflect away from oneanother and widens the access into the socket 102 sufficiently toreceive and retain the cross member 18 within the socket 102 as shown inFIG. 4. As such, the spring arms 100 provide a snap-lock coupling to thelower ribs 96. Like the upper saddles 94, the arms 100 of the lowersaddles 96 extend beyond the cross member 18 so as to overlap the uppersaddles 94.

The assembly 10 also includes ratcheting means 104 disposed within thecavity 28 about half way between the left and right side ends 38 andacting between the mounting post 14 and the headrest body 12 forpermitting the headrest body 12 to pivot forwardly relative to themounting post 14 while selectively locking the headrest body 12 againstrearward pivotal movement.

The ratcheting means 104 comprises a rack 106 disposed on one of theheadrest body 12 and the mounting post 14 and preferably on the headrestbody 12 as shown in the drawings. The rack 106 has a plurality ofdirectional one-way ratchet teeth that are formed as an integral portionof the upper section 30 of the headrest body 12. In other words, therack 106 is formed of the same material and the upper section 30. Asshown in FIGS. 3 and 7, the rack 106 extends between the front 40 andrear 42 walls with the teeth of the ratchet 106 lying along an arcuatepath and centered about the central axis of the cross member 18. Therack 106 is recessed into the top wall 36 (FIGS. 2, 3 and 7) and liesapproximately midway between the side walls 38 so as to be aligned withthe flattened region 22 of the cross member 18.

The ratcheting means 104 further includes a ratchet device 108 disposedon the other of the headrest body 12 and mounting post 14 and preferablymounted to the cross member 18 of the mounting post 14 for engaging therack teeth 106 to control the angular positioning of the headrest body12. The ratchet device 108 comprises a pawl member 110 and a pawlcarrying support member or support arm 112. The pawl member 110 ispivotally coupled to the support arm 112 by a pivoting means or pivotpin 114 and is spring biased into operational engagement with theratchet teeth of the ratchet 106 by an extension spring 116 extendingbetween the pivot pin 114 and support arm 112. As illustrated best inFIG. 6, the support arm 112 has a generally U-shape when viewed on endand includes a pair of spaced apart and generally parallel side wallportions 118 and a transverse connecting wall portion mounting post 14as shown in the drawings for engaging the rack teeth 106 to portions119. The pawl 110 is disposed between and pivoted to each of the sidewall portions 118. The support arm 112 is preferably formed from asingle piece of sheet steel which has been stamped and bent to establishthe side wall and connecting wall portions 118 120.

The ratchet device 108 and cross member 18 include self-aligning angularlocating means acting between the support arm 112 and the cross member18 for positively locating the ratchet 108 on the cross member 18 with apredetermined angular orientation relative to a central linear axis ofthe mounting post legs 16. This angular relationship is best shown inFIG. 3 wherein the support arm 112 is angled approximately 10° forwardlyof the central axis of the mounting post legs 16. The specific angularrelationship, however, may vary depending upon the application. Theangular locating means comprises the central flattened region 22 of thecross member 18 in combination with a pair of aligned slots 122 formedin the side wall portions 118 of the support arm 112. Each of the sidewall portions 118 includes a pair of spaced legs 124 defining thealigned slots 122 and presenting facing engaging surfaces 126 which arespaced substantially the same distance apart as the flats 24 of theflattened region 22. The aligned slots 122 enable the flattened region22 of the cross member 18 to be received into the slots 122 such thatthe fingers 124 straddle the flattened region 22 and the engagingsurfaces 126 of the fingers 124 intimately contact the flats 24 as shownbest in FIGS. 3 and 7. The cooperation between the flattened region 22and the slots 122 serves to self-orient the support arm 112 in itsproper angular relationship with respect to the mounting post legs 16.In other words, the straddling engagement of the fingers 124 of theflattened region prevents the support arm 112 from rotating on themounting post 14 and thereby establishes and maintains the desiredangular position. Once properly positioned, the support arm 112 issecured to the cross member 18 by a weld 128 or other suitable fasteningmeans.

As shown in FIG. 2, the ratchet device 108 is located approximatelymidway between the mounting post legs 16 aligned with the rack 106.Centrally locating the ratcheting means 104 places it more directlyalong the line of force expected to be applied to the headrest body 12during angular adjustment of the body 12 or by a user's head as a resultof a rear end collision. In either case, force is likely to be appliedcentrally to the headrest body approximately midway between the mountingpost legs 16. Positioning the ratcheting means 104 directly along theline of applied force minimizes torsion.

The side wall portions 118 of the support arm 112 include upstandingears 130 extending above the connecting wall 120 and having annularbearing surfaces 132, 134 defining a corresponding pair of alignedapertures 132, 134 extending through the side wall portions 118. Asillustrated in FIGS. 6 and 8, the aperture 134 is larger in size thanthe aperture 132, for reasons to be explained below.

The pivot pin 114 is includes a shaft-like main body having a centralpawl-engaging portion 136, first and second journaling portions 138, 140disposed on opposite sides of the central portion 136, and a pair offirst and second enlarged retaining heads 142, 144 formed at oppositeends of the pivot pin 114 adjacent the respective first and secondjournaling portions 138, 140. The pivot pin 114 extends completelythrough the apertures 132, 134 of the support arm 112 and through akeyed passage or hole 146 of the pawl 110 with the enlarged heads 142,144 engaging the outer surface of the respective side wall portions 118to retain the pivot pin 114 and pawl 110 connected pivotally to thesupport arm 112. The journaling portions 138, 140 of the pivot pin 114are rotatably supported by annular bearing surfaces 132, 134 so as toenable the pawl member 110 and pivot pin 114 to pivot as a unit about anaxis A of the pivot pin 114 relative to the support arm 112. The centralpawl-engaging portion 136 and the passage 146 have cooperating abutmentsurfaces 148, 150, respectively, which are engaged with one another toprevent the pawl 110 from rotating on the pivot pin 114. In thepreferred embodiment, the abutment surfaces 148, 150 are formed ascooperating pairs of flat surfaces on the central pawl engaging portion136 and on the walls of the passage 146. The central pawl engagingportion 136 and passage 146 are shown as having a generally rectangularcross-sectional mating configuration, but it will be appreciated thatother configurations would be suitable to prevent rotation between thepawl 110 and pivot pin 114.

As best illustrated in FIG. 8, the first head portion 142 includesself-locking fastening means for automatically locking the pivot pin 114into retaining engagement with the support 12 upon application of apush-together assembly force to the pivot pin 114 and support 112. Thefastening means comprises a pair of flexible spring fingers or tangs 152separated by a V-shaped groove which enables the head 142 to flexinwardly of itself in response to forcing the head 142 into the aperture132 so as to assume a smaller diametrical size allowing the head 142 topass through the smaller aperture 132, after which the tangs 152 areable to return to their nondeflected condition to engage the outerperipheral edge of the smaller aperture and retain the pivot pin 114connected to the support arm 112. The snap-lock head 142 is also sizedto enable it to be inserted first through the larger aperture 134, thenthrough the passageway 146 of the pawl, and finally through the smalleraperture 132 for snap-together engagement with the support 112.

The larger head 144 is formed with a spring attachment portion 154spaced from the pivot pin axis A. The associated side wall 118 issimilarly formed with a projecting spring attachment tab 156. Theaforementioned extension spring 116 is connected at one end to thespring attachment portion 154 and at the other end to the tab 156. Thespring 116 normally acts to bias the pawl 110 clockwise, as viewed inFIG. 7, so that a stopping portion 158 of the pawl 110, which is spacedfrom the pivot axis A of the pivot pin 114, engages the inner surface ofthe connecting wall 120 to limit its clockwise travel, as shown in solidlines in FIG. 7. In this position, a single tooth rack engaging portion160 of the pawl 110 is in an upright position and operatively engagingthe teeth of the rack 106. The rack engaging portion 160 includes aninclined camming surface 162 facing rearwardly of the headrest assembly10 for cooperating with inclined camming surfaces 164 of the rack teeth106. The camming surfaces 162, 164 cooperate to enable the headrest body112 to pivot forwardly in the direction of arrow F in FIG. 7. The rackengaging portion 160 further includes a locking surface 166 facingforwardly which cooperates with corresponding rearwardly facing lockingsurfaces 168 of the ratchet 106 to prevent the headrest body frompivoting rearwardly in the direction of arrow R in FIG. 7.

Biasing means, and preferably a helical torsion spring 170, isaccommodated on the cross member 18 of the mounting post 14, as shown inFIG. 5, and has one end of the spring 172 engaging and reacting againstone of the mounting post legs 16 and the opposite end of the spring 174slidingly engaging the inner surface of the rear wall portion 42 of thehead rest core 26 to continuously urge the headrest body 12 in therearward pivoting direction R to cause the locking surface 166 of thepawl to engage one of the locking surfaces 168 of the rack teeth 106 toretain the headrest body 12 in a selected position of angularadjustment. As shown in FIGS. 2 and 5, the torsion spring 170 liesbetween adjacent upper saddles 94 to limit lateral movement of thetorsion spring on the cross member 18.

To construct the headrest assembly 10, the mounting post 14 is coined toform the central flattened region 22 and then bent into the U-shape toform the legs 16 and cross member 18. The torsion spring 170 is slidonto one of the legs 16 and positioned on the cross member 18 adjacentthe appropriate leg 16. The ratchet mechanism 108 is assembled bypositioning the pawl member 110 between the side walls 118 of thesupport arm 112 and then passing the pivot pin 114 (small head 142first) through aperture 132, passageway 146 and aperture 134 whereuponthe small head 142 engages the support arm 112 with a snap-lockconnection to retain the pawl 110 and pivot pin 114 pivotally on thesupport arm 112. The extension spring 116 is attached to the pivot pin114 and support arm 112 in the aforementioned manner and the support arm112 slid on to the flattened region 22 of the cross member 18 toestablish the proper angular orientation between the support arm 112 andmounting post legs 16. The positioned support arm 112 is welded orotherwise attached to the cross member 18. The legs 16 of the mountingpost 14 are then passed through the slots 48 of the lower body section32 and the cross member 18 forced into snap-lock engagement with thelower saddles 96 so as to be retained within the sockets 102. Theheadrest cushion 86 is attached to the upper shell section 30 and theupper section 30 forced bodily into snap-locking engagement with thelower section 32 via the snap-couplings 50, 52. The couplings 50, 52maintain the saddles 94, 96 engaged pivotally with the cross member 18to enable the body sections 30, 32 to pivot together relative to themounting post 14.

As indicated in FIG. 7, a starting position (solid lines) is establishedby the headrest body 12 being disposed in a rearward-most position withthe rack engaging portion 160 of the pawl 110 disposed in front of thefirst forward-most tooth of the rack 106. The headrest body 12 is tiltedforwardly in the direction of arrow F by bodily grasping the headrestbody and rotating the body 12 so that the pawl 110 ratchets betweenadjacent teeth of the rack 106. The extension spring 116 extends alongone side of the pivot axis A and biases the pawl 110 to the uprightposition and the torsion spring 170 acts to maintain the locking surface166 of the pawl forced against the locking surface 168 of the associatedtooth to maintain the angularly adjusted position of the headrest body12.

The headrest body 12 is returned to the starting position (solid line ofFIG. 7) by tilting the headrest body 12 completely forwardly so that thecamming surface 162 of the pawl 110 engages a rearward disengagingprojection 176 formed as a continuous extension of the tooth pattern 106and also integrally formed with the upper body section 30. Thedisengaging projection 176 causes the pawl 110 to automatically rotatecounter clockwise, as viewed in FIG. 7, about the pivot axis A of pivotpin 114 so that the line of force of extension spring 116 is over-centerof the pivot axis A (i.e., the spring extends along the opposite side ofthe pivot pin axis A), thereby causing the extension spring 116 to urgeand maintain the pawl 110 in a knocked-over inoperative position, shownin phantom in FIG. 7. In this position, the pawl 110 is completelydisengaged from the ratchet 106 so that the headrest body 12 may berotated rearwardly in the direction R toward the starting position shownin solid in FIG. 7 without the pawl 110 engaging the teeth 106. Uponreaching the rearward most tilted position, the tip of the pawl 110engages the inside of the front wall 40 forcing the pawl 110 to rotateclockwise and further causing the extension spring 116 to rotate backovercenter of the pivot axis A to urge the pawl 110 into the upstandingoperational position.

The body sections 30, 32, pawl member 110, and pivot pin 114 arepreferably fabricated from organic polymeric plastic materials.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology which has been used is intended to bein the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims whereinreference numerals are merely for convenience and are not to be in anyway limiting, the invention may be practiced otherwise than isspecifically described.

What is claimed is:
 1. An adjustable headrest assemblycomprising:mounting post means (14) having a horizontal portion (18); aheadrest body (12) disposed about said horizontal portion (18); pivotconnection means (92) connecting said headrest body (12) to saidhorizontal portion (18) for enabling said headrest body to pivotrelative to said mounting post means (14); ratcheting means (104) actingbetween said mounting post means (14) and said headrest body (12) forpermitting said headrest body (12) to pivot in one direction andselectively locking said headrest body (12) against reverse pivotalmovement, said ratcheting means (104) including a rack (106) having aplurality of directional teeth and a ratchet (108) for engaging saidrack teeth (106) to control the movement of said headrest body (12); andcharacterized by said ratchet (108) comprising a support member (112)having a pair of parallel spaced side wall portions (118), a pawl (110)disposed between said side walls (118), and pivoting means (114) forpivotally coupling said pawl (110) to each of said side wall portions(118) for enabling said pawl (110) to pivot relative to said supportmember (112).
 2. An assembly as set forth in claim 1 furthercharacterized by said pivoting means (114) comprising a pivot pin (114)carrying said pawl (110) and having ends rotatably supported by saidside wall portions (118) for enabling said pawl (110) and said pivot pin(114) to rotate as a unit relative to said support (112).
 3. An assemblyas set forth in claim 2 and further characterized by said pivot pin(114) and said support (112) including self-locking fastening means(142) for automatically locking said pivot pin (114) into retainingengagement with said support (112) upon application of an assembly forceto said pivot pin (114) and said support (112).
 4. An assembly as setforth in claim 3 further characterized by self-locking fastening means(142) comprising flexible locking tangs (152) extending from one end ofsaid pivot pin (114) and an aperture (132) formed in an associated oneof said side wall portions (118), said locking tangs (152) beinginwardly deflectable in response to forcing said tangs (152) into saidassociated aperture (132) for enabling said tangs (152) to pass throughsaid aperture (132) and thereafter engage said associated side wallportion (118) for retaining said pivot pin (114) connected to saidsupport (112).
 5. An assembly as set forth in claim 4 furthercharacterized by said pivot pin (114) having an enlarged rigid head(144) formed on the other end of said pivot pin (114) for engaging theother side wall portion (118) of said support (112) to retain said pivotpin (114) connected to said support (112).
 6. An assembly as set forthin claim 5 further characterized by said pawl (110) having a passage(146) extending between said opposite sides of said pawl (110) forinsertably receiving said pivot pin (114), said passage (146) and saidpivot pin (114) having mutually engagable abutment surfaces (148, 150)for locking said pawl (110) against rotation relative to said pivot pin(114)
 7. An assembly as set forth in claim 6 further characterized bysaid locking tangs (152) o said pivot pin (114) being dimensioned forinsertion through said passage (146) of said pawl (110).
 8. An assemblyas set forth in claim 5 further characterized by said support member(112) having a connecting wall portion (120) extending between andconnecting said side wall portions (118).
 9. An assembly as set forth inclaim 8 further characterized by said pawl (110) having a stoppingportion (144) adjacent to and engagable with said connecting wallportion (120) of said support (112 to limit the pivotal travel of saidpawl (110) and a toothed rack engaging portion (162) for engaging therack teeth (106).
 10. An assembly as set forth in claim 9 furthercharacterized by said ratchet (108) including an extension spring (116)having an end thereof connected to said pivot pin (114) at a locationspaced from a pivot axis (A) of said pin (114) and an opposite endthereof connected to said support member (112), said pawl (110) beingpivotal between an upright operational ratcheting position in which saidextension spring (116) extends along a first side of said pivot pin axis(A) urging said stopping portion (144) into abutment with saidconnecting wall (120) and said rack portion (162) into ratchetingengagement with said rack teeth (106) and a layed-over inoperableposition in which said extension spring (116) extends along an oppositesecond side of said pivot pin axis (A) biasing said stopping portion(144) away from s id connecting wall (120) and said rack engagingportion (162) out of engagement with said rack teeth (106).
 11. Anassembly as set forth in claim 10 further characterized by saidextension spring (116) being connected to said enlarged head (144). 12.An assembly as set forth in claim 8 further characterized by said sidewall portions (118) extending above said connecting wall portion (120).13. An assembly as set forth in claim further characterized by said sidewall portions (118) having spaced apart legs (124) straddling saidhorizontal portion (18) of said mounting post means (14), said legs(124) and said horizontal portion (18) having mutually engaging surfaces(126, 124) for preventing relative rotation between said support (112)and said mounting post means (14).